1. Field of the Invention
The present invention relates to a high-pressure piston pump for liquids, preferably for water, which includes a valve control through a suction and pressure valve, in which the pump pistons are movable at least in the pressure direction through the intermediary of a hydraulic drive.
2. Discussion of the Prior Art
Known liquid pumps, particularly water pumps, are constructed as plunger pumps with valve control. The drive and the movement of the pistons is generally effected through a crank mechanism. A pressure regulation of pumps of that type is effectuated either through a by-pass control, torque converter, rotational speed-regulated direct-current drive or double-swing drive. Directly influenced by the last-mentioned type of drive is the piston stroke and, as a result, the discharge pressure.
Also known is a pump construction for liquid pumps of that type in which the pistons, as in an axial piston pump, are arranged about a central axis. This type of construction facilitates a simple regulation of the piston stroke. However, encountered herein is the problem in the lubrication of the drive elements of such an axial piston machine. In order to ensure the trouble-free function of a pump which is constructed in that manner, a lubricating medium pressure must be built up within a special lubricating medium circuit which is proportional to the liquid pressure.
A piston pump of the above-mentioned type has become known, for example, from German Published Patent Application No. 1 019 563. Therein, the pump pistons of the liquid pump are driven through a hydrostatic drive, consisting of an axial piston pump and hydraulic operating cylinders, which stand in communication with the pump pistons. A piston pump which is driven in that manner can be regulated only through considerable constructional demands on the stroke volume and thereby in the discharge pressure. For a steam or compressed-air pump there must be provided the usual pilot control system.